A processing system adapted for processing an object to be processed, including a processing vessel configured for containing the object to be processed and for receiving a processing fluid, a processing fluid generating unit configured for generating a processing fluid, a processing-side fluid passage configured for supplying the processing fluid into the processing vessel, and a discharge fluid passage configured for discharging the processing fluid from the processing vessel. The processing system further includes a bypass-side fluid passage configured for discharging the processing fluid generated in the processing fluid generating unit without passing it through the processing vessel, a pressure control mechanism provided to the discharge fluid passage downstream from a position at which the bypass-side fluid passage is connected with the discharge fluid passage, and a switch valve configured to selectively switch a fluid passage of the processing fluid between the processing-side fluid passage and the bypass-side fluid passage.